You have a solution of sodium iodide (Nal) and need to add something to it that will precipitate the iodine ions out while leaving the sodium ions in solution. According to the solubility chart below, which of these compounds would accomplish that?
A. Aluminum
nitrate (AIZNO3)

B. Silver nitrate
(AgNO3)

C. Sodium phosphate
(NazP04)

D. Sodium nitrate
(NaNO3)

answer : third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol

explanation :

let us write down the given equations

equation 1 :

equation 2 :

equation 3 :

let us use hess's law to find out which 2 equations can be added to get the third equation.

let us reverse equation 2 and multiply it by 2. the new equation that we get is,

equation 4 :

let us add equation 1 & 4

the above equation is similar to equation 3 but has different value for dhrxn.

therefore third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol